Redo StreamTransformers so they work with Stack traces.

tests/lib/async/stream_transformer_from_handlers_test.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:expect/expect.dart';
+import 'package:async_helper/async_helper.dart';
+import 'dart:async';
+import 'event_helper.dart';
+
+
+get currentStackTrace {
+  try {
+    throw 0;
+  } catch (e, st) {
+    return st;
+  }
+}
+
+// In most cases the callback will be 'asyncEnd'. Errors are reported
+// asynchronously. We want to give them time to surface before reporting
+// asynchronous tests as done.
+void delayCycles(callback, int nbCycles) {
+  if (nbCycles == 0) {
+    callback();
+    return;
+  }
+  Timer.run(() {
+    delayCycles(callback, nbCycles - 1);
+  });
+}
+
+main() {
+  // Make sure the generic types are correct.
+  asyncStart();
+  var stackTrace = currentStackTrace;
+  var events = [];
+  var controller;
+  controller = new StreamController(onListen: () {
+    controller.add(499);
+    controller.addError(42, stackTrace);
+    controller.close();
+  });
+  controller.stream
+    .transform(
+        new StreamTransformer<int, String>.fromHandlers(
+            handleData: (int data, EventSink<String> sink) {
+              sink.add(data.toString());
+            },
+            handleError: (e, st, EventSink<String> sink) {
+              sink.add(e.toString());
+              sink.addError(e, st);
+            },
+            handleDone: (EventSink<String> sink) {
+              sink.add("done");
+              sink.close();
+            }))
+    .listen((data) => events.add(data),
+        onError: (e, st) {
+          events.add(e);
+          events.add(st);
+        },
+        onDone: () {
+          Expect.listEquals(["499", "42", 42, stackTrace, "done"],
+                            events);
+          delayCycles(asyncEnd, 3);
+        });
+}